Heterostylum hirsutum

Heterostylum hirsutum (Thunberg)

Material examined. New records. ARGENTINA. Buenos Aires: Villalonga (40°03′S, 62°29′W), 12.i.2018, ex Medicago sativa, J.P. Haedo & H.J. Marrero (2 ♀, FAUBA); Villalonga, 12.i.2018, ex Centaurea solstitialis, J.P. Haedo & H.J. Marrero (1 ♂, FAUBA); Villalonga, 27.xii.2018, ex Medicago sativa, J.P. Haedo & H.J. Marrero (1 ♀, MACN); Villalonga, 8.i.2019, ex Medicago sativa, J.P. Haedo & H.J. Marrero (1 ♀, MACN). Formosa: San Francisco de Laishi: Reserva El Bagual (26°18′S, 58°49′W), 19.xi.2012, J.P. Torretta (1 ♀, MACN); San Francisco de Laishi: Reserva El Ba- gual (on one large nest aggregation of Diadasina distincta), 8.i.2014, J.P. Torretta (3 ♀, FAUBA).

Distribution. Argentina (La Rioja, Buenos Aires and Formosa. New records), Brazil (Mato Grosso do Sul), Colombia (Magdalena), Venezuela (La Guaira) (Fig. 1).

Remarks. Two new provincial records for this species are presented here from Argentina, Formosa and Buenos Aires. Four female individuals were captured with sweep nets in the Reserva El Bagual (Fig. 1), in Formosa province. The Reserva El Bagual consists of ca. 3,700 ha and is an open savanna located to the east of the humid Chaco region, with different forest types covering diverse environments (Maturo et al. 2005). Three females were captured hovering and ejecting eggs on one large nest aggregation of Diadasina distincta (Holmberg) (Apidae: Emphorini). We were unable to determine if H. hirsutum successfully parasitized the brood cells of D. distincta, but if confirmed this would represent the first host record for this bee fly species. This site is intermediate to the previous records for the southern populations of the species (La Rioja in Argentina and Mato Grosso in Brazil) and close to Paraguay. Lamas et al. (2014) commented that H. hirsutum was recorded in Paraguay, but they could not confirm its presence based on material examined in collections and literature review.

The other five specimens of this species were captured in Villalonga, south of Buenos Aires province (Fig. 1). This region is located south of the Monte ecoregion and the predominant land use is agricultural-livestock and the main crops are onion (Allium cepa L.) and lucerne (Medicago sativa L.) (Torretta et al. 2021). Four females were collected feeding on nectar from flowers of lucerne and one male from one flowerhead of yellow star-thistle (Centaurea solstitialis L.), a common exotic weed in this region. This site is more than 1,000 km from La Patquía (La Rioja), the previous locality from the Monte ecoregion where H. hirsutum was captured and represents the austral-most geographic record for Heterostylum.

In summary, in this paper we increase to four the number of species of Heterostylum recorded from Argentina, expand the austral-most distribution record of the genus by more than 1,000 km and tentatively propose Diadasina distincta (Apidae: Emphorini) as a possible host for H. hirsutum.